Date seed as an industrial waste; effect of roasting on antioxidant capacity of date seed flour and date seed coffee brews

Date is one of the historical plant which has been grown by humankind. This plant has been playing vital role in both North Africa's and Middle East's economy. It was transported to America by Spanish at the begining of 19th century and was farmed in Mexico. In Turkey, dates which in East and South Mediterranean are consumed in high quality by Turkish people. Evidence of date palm cultivation goes as far back as 4000 BC in what is now southern Iraq. The date palm is found in the Near East, North Africa, and the American continent, where dates are grown commercially in large quantities. The botanical name of the date palm is Phoenix dactylifera L., and it is an important member of the family Palmacea. There are over 2000 different date varieties, which vary in shape, size, and weight. Usually they are oblong in shape, although certain varieties may be almost round. The length ranges from 1.8 to 11.0 cm, and the width from 0.8 to 3.2 cm; the average weight per fruit is 2-60 g. As with the fruit, the seed characteristics also vary greatly according to variety, and environmental and growing conditions. Date seeds, also called stones or pits, form part of the integral date fruit, which is composed of a fleshy pericarp and seed that constitutes between 10 and 15% of the date fruit's weight, depending on the variety and quality thus, approximately 825,000 tons of date seeds are produced annually. The seed weight ranges from 0.5 g to 4 g, the length from 1.2 to 3.6 cm, and the width from 0.6 to 1.3 cm. The seed is usually oblong, ventrally grooved, with a small embryo, and with a hard endosperm made of a cellulose deposit on the inside of the cell walls. As it is also known that date seeds contain valuable bioactive compounds, utilization of this by-product is highly desirable for the date industry. Seed of date is a cheap fiber in the diet and considered as a potential source of antioxidants. As such seeds can be used as functional food additives. Moreover, milled seeds are consumed as decaffeinated coffee by Arabs. Furthermore, date seeds are considered as waste and used as animal feed. Epidemiological studies have consistently shown that high fruit and vegetable consumption is associated with a reduced risk of several chronic diseases, such as coronary heart disease, cardiovascular disease, cancers, atherosclerosis, neurodegenerative diseases (such as Parkinson and Ahlzeimer), and inflammation, as well as aging. This is attributed to the fact that these foods may provide an optimal mixture of phytochemicals such as dietary fiber, natural antioxidants such as vitamins C, E, and beta-carotene, and phenolic compounds. Interestingly, the peel and seed fractions of some fruits possess higher antioxidant activity than the pulp fraction . Date seeds appear to fit well into this category. Several studies have reported the advantages of the incorporation of date seeds into animal diets. Some of these advantages include increased weight gain, improved feed efficiency, and improved meat palatability. Adding date seed to the starter and finisher diets improved body weight gain, feed conversion, and growth performance, comparable to the cornesoybean meal diet of broiler chicks. Results show that the date seed can be included at 10% in broiler diets to support and enhance growth performance. Also, studies show that a feeding treatment with normal date seeds (7-14%) significantly increased the testosterone in plasma, and the body weight of rats. The protein of date seeds has a higher concentration of lysine, which is often the limiting amino acid in diets based on cereals. In this study, mebrun type dates were used and the seeds of mebrun dates were roasted in different times (5 min, 10 min, 15 min) at constant tempreture (2000C) with precision coffee roaster. Then, roasted and unroasted seeds were milled. Extracts for the usage in the assay were prepared. 80% ethanol was used as suitable solvent on the basis of liteature. Total phenolics and total antioxidant activity in roasted coffee powder, unroasted seed flour and the brews from roasted powders were measured by spectrophotometric analysis. Total phenolics were determined by Folin- Ciocalteu method. Results were expressed by mg gallic asid/ 100 g dry matter. In order to determine the antioxidants activity; DPPH Free Radical Scavenging Capacity and Cupric Reducing Antioxidant Capacity assays were performed. Results were expressed through TROLOX equvalent. Total phenolic content and total antioxidant capacity values indicated that seed flour were significantly higher. When compared to rosted and unroasted flour, total phenolic content decreased with roasting effect. Same results were obtained from brew samples. Unroasted brews showed the highest total phenolic content and antioxidant capacity and 15 min. roasted brews showed the least TPC and antioxidant capacity. In regards to the total antioxidant capacity methods, CUPRAC assay gave higher responses than the DPPH assay in accordance with the literature. The corrlation coefficients between the assays were calculated and the significance of the assays were statistically analyzed. The bioaccessibility of phenolics from roasted and unroasted powder and brews was assessed by in vitro gastro-intestinal digestion procedure that simulates the physiochemical and biochemical changes that occur in the gastrointestinal tract. Since in vivo studies on humans and animals are not preferred due to the limitations such as complexity, expensiveness and ethical reasons, in vitro digestion assays provide rapid and simple methods to evaluate phytochemical stability in food matrices. Samples were collected prior to digestion (initial), after gastricdigestion (post-gastric, PG), and after intestinal digestion (serum-available, IN; nonserum-available, OUT) and analyzed using spectrophotometric assays. The percent recoveries were calculated as the proportions of the values obtained for PG, IN and OUT fractions to the initial values. Results from in vitro digestion demonstrated that phenolic acids were found to be stable in gastric digestion due to acidic conditions. At the end of the study, date seeds appeared to have a high phenolic content and antioxidant capacity However, they were affacted by the high content roasting and showed reduction in the antioxidant capacity and total phenolic content.